The present invention is related to a modular arrangement of directional RF filters employed to provide multiplexing of a plurality of earth station transmitters which transmit on two orthogonal polarizations.
Ground stations adapted for communication with a plurality of diverse frequency satellite transponders must accommodate a wide spectrum of frequencies. Each of the satellite transponders may, for example, have a frequency band over approximately 36 MHz, with an additional guard band of 4 MHz. Thus, a ground station which must communicate with a satellite having 12 transponders, for example, must necessarily operate at least over a 480 MHz (40 MHz.times.12) band.
In frequency reuse systems, a doubling of the information carrying capacity of a system is achieved by separating signals having the same frequency on the basis of polarization. Thus, in the above described communication system, the earth station may communicate with a satellite transponder having 12 vertically polarized and 12 horizontally polarized transponders.
In such frequency reuse systems, the ground station transmitters in accordance with commonly used techniques are provided in one of two ways. First, a single wide-band power source covering the entire frequency spectrum may be employed for each polarization. However, such wide-band sources are expensive and inefficient when operated at the back-off required for multiple carrier transmission. Secondly, a plurality of frequency sources may each be multiplexed for the individual polarizations. This, however, requires the use of two multiplexers, one for each of the vertically and horizontally polarized transmissions.